APPLICANT'S ABSTRACT: Although much has appeared in worldwide literature about different approaches to syringe use and control, there have been no studies of two sites in which different policies on accessibility of injection paraphernalia exist. Two funded studies conducted by investigators in Miami and Valencia afford unique opportunities to conduct parallel ethnographic studies that compare sites in terms of availability of syringes to intravenous drug users (IDUs). Miami and Valencia have several characteristics (port cities, bilingual, multiethnic, dominance of cocaine among others) that make comparative study seem appropriate, especially since they have very different official policies on availability of syringes. Pharmacies in Valencia may sell syringes to all customers, while pharmacies in Miami may sell only to prescription holders. Studies proposed here will investigate five research questions regarding differential seroprevalence in the two sites and they will focus on similarities and differences in risk behavior among IDUs in Miami and Valencia in order to formulate strategies for prevention in both cities.